This invention relates generally to the field of composite materials and, more particularly, to gas-impermeable composite materials which include basalt and are intended for use in high pressure applications.
Pressure vessels are used in many industries to store gasses under nigh pressures. These pressure vessels are generally constructed out of carbon-based composites, namely, a high strength plastic reinforced with carbon fiber filaments. The carbon fiber filaments are costly to manufacture and must go through a variety of resource-intensive processes which, in turn, produce a variety of hazardous byproducts. The manufacturing process involves a filament winding process in which a fiber tow is first impregnated with a matrix resin and then applied at predetermined angles to a rotating liner or mandrel (which is typically made of aluminum or high-density polyethylene). After the impregnated fibers are applied, the structure must be cured, usually by heat.
By way of example, a composite pressure vessel used for high pressure cryogenic storage is disclosed in U.S. Pat. No. 7,867,589 to DeLay. The inner layer of the vessel is a matrix of fiber (e.g., aramid fiber) and polyurethane resin. The outer layer encapsulates the inner layer, provides structural support to that layer, and is a matrix of fiber (e.g., aramid or carbon fiber) and resin (e.g., high ductability resin or polyurethane matrix that performs well at low temperature). Once the inner and outer layers are cured, the mandrel is removed. Because this vessel is designed to contain a liquid stored at low temperatures, it does not require an impermeable barrier. Therefore, the vessel can make use of carbon (or aramid) fibers and foregoes a metal or polymeric liner. There is a need for a high pressure, liner-free vessel for storing compressed natural gas that does not rely upon carbon or aramid fibers, is more easily manufactured than those carbon- and aramid-fiber based vessels, does not involve the manufacturing step of collapsing the mandrel after the vessel material has been cured, and is lighter weight and smaller than metal pressure vessels of equivalent size and pressure ratings.